1. Field of the Invention
This invention relates to a linear fluid motor comprising a piston mounted on a rod and arranged for the piston to reciprocate in an outer cylinder member, and more specifically to such a motor which is hydraulically operated.
2. Description of the Prior Art
Linear hydraulic motors are utilized in a variety of applications in machines and vehicles to accomplish power operation and/or remote control of parts and components, the operation or remote control being accomplished by an operator controlling the supply of pressurized hydraulic fluid to the motor from a valve at an operator's station.
Various constructions have been utilized for securing the piston to the rod end in such motors and one of these is a threaded or screw type connection. One form of screw type connection comprises internal threads in an opening through the center of the piston and mating external threads on the rod which extends through the piston. Another known form of screw type connection uses a threaded engagement between external threads on the rod and internal threads on a lock nut which is disposed adjacent to the piston and bears against it, holding it in the desired position on the rod.
Such motors may be subject to frequent operation and may operate at pressures of 2500 pounds per square inch or more. In such motors manufactured heretofore with normal tolerances and clearances there have been various problems and among the most serious are the problems caused by abnormal distribution of lateral forces resulting from misalignment between the piston and cylinder during some conditions of operation. Such misalignment increases the friction, may cause noise, may allow dirt to be trapped, and cause undue wear of the piston and/or cylinder, and leaking.
Numerous constructions have been utilized heretofore in an attempt to provide a suitable connection between the piston and rod of a linear hydraulic motor and in many of such constructions it has been attempted to secure and hold the piston and rod rigidly together so that they act as an integral reciprocal member, even though such a rigid connection serves to perpetuate any initial misalignment. With normal or even extraordinary manufacturing tolerances the alignment of the piston on the rod and the piston with the cylinder is not perfect, when the piston and rod are rigidly connected together, and the result is abnormal distribution of lateral forces between the piston and cylinder under some circumstances with the resulting deleterious consequences.